More than 70% of AIDS patients have cardiac abnormalities with 30% mortality. Opportunistic infection and tumor have been cited as the major causes. Many inflammations in the hearts of AIDS patients have no identifiable etiology. In a preliminary study, we have found that HIV-1 core proteins pl7- and p24-like immunoreactivities and envelope protein gpl6O-like immunoreactivity were present in myofibrils of the myocardiocytes in the heart of HIV infected patients (n=5) but not of non AIDS patients (n=6). We plan to conduct a study on the hearts of 100 AIDS patients and 20 non AIDS patients. The possible presence and distribution of the HIV proteins, gpl6O, p2, pl7, and reverse transcriptase in the heart will be studied with the techniques of immunocytochemistry using monoclonal antibodies. The possible presence of HIV-1 nucleotide sequence will be investigated with tissue in situ hybridization. The subtypes of infiltrating cells particularly those bearing the receptor CD4 molecule will be examined by immunocytochemistry. The morphological changes and the presence of pathogens in the hearts will be studied by conventional light and electron microscopies. This study will provide a morphological basis for the pathogenesis of the cardiac complications in AIDS. The establishment of the presence of HIV-1 elements, either proteins or nucleotide sequences, in the cardiomyocytes of AIDS patients will change the current view on the pathogenic mechanism of AIDS and reveal a new dimension in understanding, prevention, and treatment of AIDS and AIDS related cardiac complications.